NO309498B1 - Brönnverltöy including an anchoring device with arms that are pneumatically unfoldable and hydraulically retractable - Google Patents

Description

The present invention relates to a well tool including a tool body which is designed with an elongated cavity, which tool is immersed in a well, connected to a surface installation via an electricity-carrying cable, at least one anchor element such as an articulated, in relation to the tool body movable arm, as well as displacement means for intermittent movement of each anchor element between a retracted position close to the body and an extended position where it is anchored in the well wall, which displacement means comprise, in the tool body, a hydraulic pump which is activated by means of an electric motor, a piston which sealingly divides an elongated cavity in the body in a first and a second chamber, the piston being displaceable in the cavity under the influence of a first force which is used to move each anchor element to its extended position and a second counteracting force to return each anchor element to its retracted position.

A well tool of the above kind can e.g. be equipped with seismic sensors such as geophones for collecting seismic waves of P or S type, which are transmitted by a seismic energy source such as e.g. is located at the surface and which is reflected by underground discontinuities.

The tool is e.g. equipped with measuring equipment intended for studying the geological formations encountered, or for carrying out seismic mineral surveys in formations intersected by the borehole.

The tools are immersed in the drill holes at the end of a cable, which is usually an electricity-carrying cable. They are usually equipped with one or more swing arms that can be opened or closed as desired by means of propellants. By e.g. geophysical applications, the seismic sensors are placed so that they are pressed with sufficient force against the borehole wall when the anchor arms are opened. To achieve an adequate connection, the anchoring force is usually several times greater than the weight of the tool.

US 4 365 668, US 4 428 422, US 4 557 326, US 4 616 703, US 4 926 937, US 5 127 477 and US 5 259 452 can be mentioned as examples of the state of the art with regard to hydraulic or pneumatic operation of anchoring arms. .

The propellants which act to swing the arms can be of the hydraulic type. An electric motor controlled from a surface installation drives a hydraulic pump that delivers fluid under pressure to either a single power cylinder acting on the swing arms via articulated joints, or power cylinders acting directly on the swing arms. The force applied to the arms is independent of their distance from the tool body.

These propellants can also be electromechanical means and include e.g. an endless screw that is rotated using an electric motor that is also controlled from the surface. A nut to which is attached one or more links which are connected to the swing arms is caused to move by means of the rotation of the screw. For safety reasons, so that the arms are always retracted even when the drive motor is stopped, the joint ends can be attached to a ring on which a spring rests. The spring force acts to push the ring and to trigger swinging of the arms. The motor is only used to close the arms. The movement of the nut, controlled by the rotation of the worm screw, acts to move the nut away and to compress the spring. If the motor stops, the recoil of the ring, combined with the compression of the spring, will allow the arms to move closer.

These elastic joint devices have the disadvantage that the springs which are necessary to achieve a high support force, e.g. in the geophysical area, which are often heavy and bulky, which complicates the construction of tools of relatively small cross-section that match the cross-section of the wells that are generally drilled.

The present invention aims to remedy this disadvantage, and this is achieved by a well tool of the kind indicated at the outset, in that the well tool comprises a pressurized gas reserve for creating the first force in the second chamber by expansion of the gas, the second counteracting power is generated in the first chamber by means of a hydraulic fluid which is supplied by means of the hydraulic pump, under the control of a solenoid valve. Advantageous embodiments of the well tool according to the invention are specified in the subsequent claims.

The well tool according to the invention thus enables intermittent anchoring of a tool or a probe that is submerged in a well, connected to a surface installation via an electricity-carrying cable, by displacing an anchor element such as an articulated, movable arm in relation to the tool body, between a retracted position close to the body and an expanded position, without the disadvantages associated with the use of springs to create elastic opening forces.

The invention shall be described in more detail below with reference to the accompanying drawings, where:

Figure 1 schematically shows a section through the tool body equipped with the maneuvering device, Figure 2 shows an example of a curve for the variation of the force F1 which is developed by the gas volume as a function of the displacement of the piston X, for a first value VM1 = 0 of the dead volume VM (the gas volume behind the piston in tension position), and Figure 3 shows another example of curve P for variation of the force developed by the gas volume as a function of the displacement of the piston X for another value VM2 = 110 cm<3> of the dead volume, and for comparison the linear variation curve M for the force developed by a mechanical spring.

The tool or probe body 1 is immersed in a well 2 suspended in an electrically conducting multi-conductor cable 3 of a known type. It can be firmly pressed against the wall by turning at least one and preferably two anchoring arms 4 from a retracted position in contact with the body, to an extended position 41 and released by an opposite movement. The movements of each anchoring arm 4 are controlled by the translational movement of a link 5 in a cylinder 6 arranged perpendicular to the longitudinal axis of the tool 1.

In a cylindrical cavity 7 which is arranged along the longitudinal axis of the body 1, a piston 8 is displaceably arranged which is provided with seals 10 which tightly separate the cavity into two chambers 7a, 7b. The first chamber 7a is filled with liquid and communicates via channels 11 which are provided with a control solenoid valve (not shown), with a second cavity 12 containing a hydraulic pump 13. This pump 13 is operated by an electric motor 14 which by means of conductors 15 are connected to the electricity-producing cable's 3 conductors. The second chamber 7b, on the other side of the piston 8, contains a gas under pressure.

The rod 9, on either side of the piston 8, moves in a sealing manner in two coaxial chambers 16a, 16b which form the extension of the first cavity 7 respectively at its two opposite ends and whose cross-section is smaller than the cross-section of the two chambers 7a , 7b.

On the side of the first chamber 7a, the chamber 16a is filled with hydraulic fluid and communicates with each cylinder 6 via a channel C. The cross-section of the channel C is chosen sufficiently small to form a low-pass filter that prevents the vibrations to which it may be exposed by transfer through the anchoring arms 4, is transferred to the piston 8 and the gas mass in the chamber 7b.

The chamber 16b communicates permanently with the pump's cavity 13. The pressure in the pump's 13 hydraulic fluid is permanently maintained at a pressure equal to the hydrostatic pressure that prevails in the well, by means of an equalizing cylinder 17 with an opening to the outside of the body 1, where a freely movable stamp 18.

In a tension position where the gas is maximally compressed, the piston 8 rests against a stop 19.

The vibration sensors 20, e.g. a three-axis geophone or triphone is preferably placed in housing 21 near at least one of the points where the anchoring force that presses the tool body 1 against the wall of the well 2 is exerted. The sensors 20 are connected via conductors (not shown) to an amplifier and filtering module 22 which is arranged in a compartment 23 in the body. When several tools or probes are immersed in a well in the form of a string, a communication module 24 is placed which is intended for coding and decoding of data (control signals from the surface station and response signals emitted by the well equipment) which is transmitted through the wires of the electricity-carrying cable 3, in compartment 23 on the top probe (closest to the surface).

Mode of action:

The tool (or possibly the tool string) is immersed in the well. As soon as it has reached a depth where measuring operations are to be carried out, the solenoid valve is signaled to open each channel 11, which releases each piston 8 from the hydraulic pressure which holds it in a tense position against the stop 19. The compressed gas in the chamber 7b will then push back the piston 8 which compresses the fluid in the chamber 7a. The gas pressure is consequently transferred to the fluid in the cylinders 6 and the joints 5 are readjusted, which causes the arms 4 to open until they are anchored against the wall of the well 2. Figure 3 shows the variation curves for the anchoring force as a function of the displacement of the piston, one, P , developed by a mass of gas (dead volume 110 cm<3>), the other, M, by a much larger mechanical spring of diameter 8 cm, length 20 cm and formed by a thread of diameter 1 cm. It should also be noted that the pneumatic spring used is more efficient than such a mechanical spring within a relatively long extension range. The use of this pneumatic spring thus simplifies the construction of the tool body. When operations in progress at this stop depth are finished and the tool or tool string is to be moved to another depth, the power supply of the electric motor 14 receives a signal to increase the pressure in the hydraulic fluid supplied by the pump 13 and bring the piston 8 back towards the stop 19. Each solenoid valve which controls the channels 11 are then closed.

Due to the elasticity of the pressurized gas in the chamber 7b, the arms in the open position have a certain freedom of movement, so that the tool can still be brought up to the surface in the event that the electric motor-hydraulic pump unit 13, 14 for one reason or another does not respond or deliver the required pressure.

By changing the ratio between the maximum volume of the chamber 7b and the dead volume (the minimum volume of the chamber 7b when the piston 8 is pressed against the stop 19), the stiffness of the spring constituted by the gas can be varied in significant proportions. One can choose an operating zone where the stiffness K, which is the value of the slope of the curve (figure 2), varies mainly with the extension (zone A), or another (zone B), where it is mainly constant.

The stiffness K can be varied by means of an adjustable stop 19, or by placing one or more disks in the annular chamber 7b to thereby reduce the dead volume.

The anchoring force depends on the gas pressure in the chamber 7b. It can easily

is modified by changing the gas introduction pressure, either at the surface prior to submersion of the tools, or during operations from a gas accumulator (not shown) which is brought under high pressure and placed in the tool body. The device also preferably includes control means, not shown, which make it possible to regulate the pressure in the chamber 7b to take into account the variations in the temperature prevailing in the well, either by releasing gas from the body 1, or by introducing it from the gas accumulator, thereby achieving a preferably largely uniform anchoring force.

One can easily verify that the volume of gas required to achieve an anchoring force equal to several times the weight of the tool or probe is relatively low (of the order of 100 to 200 cm<3>) compared to the volume that a spring was capable of to provide an equally large anchoring force would have occupied.

Without deviating from the scope of the invention, each movable arm 4 can be replaced by any equivalent anchoring element: piston, shoe, etc., which can be displaced by the action of the joints 5.

Without deviating from the scope of the invention, a single, combined hydraulic-pneumatic maneuvering device as described above can be used, placed in a main probe body, for controlling the opening of the arms of several satellite probes which are connected to the main probe by means of connecting means as described e.g. . in the patents FR 2 636 741 and FR 2 685 139.

Claims (9)

1, Well tool (1) comprising a tool body which is designed with an elongated cavity, which tool is immersed in a well (2), connected to a surface installation via an electricity-carrying cable (3), at least one anchor element (4) such as an articulated , in relation to the tool body movable arm, as well as displacement means for intermittent movement of each anchor element (4) between a retracted position close to the body and an extended position where it is anchored in the well wall, which displacement means comprise, in the tool body (1), a hydraulic pump ( 13) which is activated by means of an electric motor (14), a piston (8) which sealingly divides an elongated cavity (7) in the body into a first and a second chamber (7a, 7b), the piston (8) being displaceable in the cavity (7) under the influence of a first force which is used to move each anchor element (4) to its extended position and a second counteracting force to return each anchor element (4) to its retracted position, character raised in that the well tool (1) comprises a pressurized gas reserve for creating the first force in the second chamber (7b) by expansion of the gas, the second counteracting force being generated in the first chamber (7a) by means of a hydraulic fluid which is supplied by using the hydraulic pump (13), under the control of a solenoid valve. 2, Well tool according to claim 1, characterized in that the displacement means (13, 8) for each anchor element (4) comprise a hydraulic cylinder (6) which occupies a displaceable joint (5), and that the piston (8) comprises a rod (9) which is sealingly displaced in a chamber (16a) which is filled with a hydraulic fluid, which chamber (16a) communicates with each hydraulic cylinder. 3. Well tool according to one of the preceding claims, characterized in that the pump (13) is placed in a chamber (12) in the tool body which communicates with a compensation chamber (17, 18) for permanent adjustment of the pressure of the hydraulic fluid in the chamber (12) to the pressure prevailing on the outside of the tool (1). 4. Well tool according to one of the preceding claims, characterized in that it comprises means for modifying the stiffness of the spring which is constituted by the gas volume in the second chamber (7b). 5. Well tool according to the preceding claim, characterized in that the means for modifying the stiffness comprise an adjustable stop (19). 6. Well tool according to claim 4, characterized in that the means for modifying the stiffness comprise elements placed in the second chamber to thereby vary its volume. 7. Well tool according to one of the preceding claims, characterized in that it comprises means for regulating the gas pressure in the second chamber (7b). 8. Well tool according to claim 1 or 2, characterized in that it also includes a housing for sensors (20) and at least one cubicle (21) for electronic means for processing the signals emitted by the sensors (20). 9. Well tool assembly according to claim 8, characterized in that it comprises several well tools (1), each of which is equipped with an anchor device.